/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package com.tlf.dyjc5.servlet.system;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 *
 * @author Administrator
 */
public class Checkcode extends HttpServlet {

    // 设置图形验证码中字符串的字体和大小  
    private Font myFont = new Font("Arial Black", Font.PLAIN, 16);  
  
    @Override  
    public void init() throws ServletException {  
        super.init();  
    }  
  
    // 生成随机颜色  
    Color getRandColor(int fc, int bc) {  
        Random random = new Random();  
        if (fc > 255)  
            fc = 255;  
        if (bc > 255)  
            bc = 255;  
        int r = fc + random.nextInt(bc - fc);  
        int g = fc + random.nextInt(bc - fc);  
        int b = fc + random.nextInt(bc - fc);  
        return new Color(r, g, b);  
    }  
  
    @Override  
    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  
  
        // 阻止生成的页面内容被缓存，保证每次重新生成随机验证码  
        response.setHeader("Pragma", "No-cache");  
        response.setHeader("Cache-Control", "no-cache");  
        response.setDateHeader("Expires", 0);  
        response.setContentType("image/jpeg");  
        // 指定图形验证码图片的大小  
        int width = 80, height = 20;  
        // 生成一张新图片  
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);  
        // 在图片中绘制内容  
        Graphics g = image.getGraphics();  
        Random random = new Random();  
        g.setColor(getRandColor(200, 250));  
        g.fillRect(1, 1, width - 1, height - 1);  
        g.setColor(new Color(102, 102, 102));  
        g.drawRect(0, 0, width - 1, height - 1);  
        g.setFont(myFont);  
        // 随机生成线条，让图片看起来更加杂乱  
        g.setColor(getRandColor(160, 200));  
        for (int i = 0; i < 155; i++) {  
            int x = random.nextInt(width - 1);// 起点的x坐标  
            int y = random.nextInt(height - 1);// 起点的y坐标  
            int x1 = random.nextInt(6) + 1;// x轴偏移量  
            int y1 = random.nextInt(12) + 1;// y轴偏移量  
            g.drawLine(x, y, x + x1, y + y1);  
        }  
        // 随机生成线条，让图片看起来更加杂乱  
        for (int i = 0; i < 70; i++) {  
            int x = random.nextInt(width - 1);  
            int y = random.nextInt(height - 1);  
            int x1 = random.nextInt(12) + 1;  
            int y1 = random.nextInt(6) + 1;  
            g.drawLine(x, y, x - x1, y - y1);  
        }  
  
        // 该变量用来保存系统生成的随机字符串  
        String sRand = "";  
        for (int i = 0; i < 4; i++) {  
            // 取得一个随机字符  
            String tmp = getRandomChar();  
            sRand += tmp;  
            // 将系统生成的随机字符添加到图形验证码图片上  
            g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));  
            g.drawString(tmp, 15 * i + 10, 15);  
        }  
  
        // 取得用户Session  
        HttpSession session = request.getSession(true);  
        // 将系统生成的图形验证码添加  
        session.setAttribute("rand", sRand);  
        g.dispose();  
        // 输出图形验证码图片  
        ImageIO.write(image, "JPEG", response.getOutputStream());  
  
    }  
  
    // 随机生成一个字符  
    private String getRandomChar() {  
        int rand = (int) Math.round(Math.random() * 2);// 将0～2的小数四舍五入生成整数  
        long itmp = 0;  
        char ctmp;  
        // 根据rand的值来决定是生成一个大写字母、小写字母和数字  
        switch (rand) {  
        // 生成大写字母的情形  
        case 1:  
            itmp = Math.round(Math.random() * 25 + 65);  
            ctmp = (char) itmp;  
            return String.valueOf(ctmp);  
            // 生成小写字母  
        case 2:  
            itmp = Math.round(Math.random() * 25 + 97);  
            ctmp = (char) itmp;  
            return String.valueOf(ctmp);  
            // 生成数字  
        default:  
            itmp = Math.round(Math.random() * 9);  
            return String.valueOf(itmp);  
        }  
    }  
}  
